Understanding the distributions of rare pollinators is necessary to guide monitoring and inform species recovery efforts. We tested a novel approach for finding undiscovered populations of the endangered rusty patched bumble bee in the Midwestern U.S. Our research team discovered rusty patched bumble bees at over 50% of the grid cells we surveyed, suggesting our methods were effective for finding undiscovered rusty patched bumble bee sites. We highlight the utility of our approach for guiding future survey efforts by identifying an additional 145 grid cells where the occupancy status of rusty patched bumble bee is unknown, but we predict a relatively high likelihood of rusty patched bumble bee occurrence. Our approach can be extended to find undiscovered rusty patched bumble bee sites in other areas and applied to other bee species where occurrence information is lacking outside of their core distribution. We also highlight the development of eDNA methods for finding undiscovered populations of hard-to-find pollinators. Our results indicate that eDNA works about as well as traditional visual surveys at finding rare bee species if the correct flowering plant species are sampled.